Venus was once more Earth-like than previously thought

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Thursday, November 29, 2007

Artist's impression of Venus Express orbiting Venus. Image credit: ESA.

New data from the European Space Agency's Venus Express mission suggest that Venus was once Earth-like but later evolved in a different way. The findings, published in the journal Nature on Thursday, also confirm that there is lightning on Venus.

"The two planets were, in fact, very similar in the earlier days of the solar system," said Venus Express team scientist Hakan Svendem, "And they have then evolved in different directions, but according to the same rules and explanations." Professor Fred Taylor of the University of Oxford, another scientist on the mission, said "Our new data make it possible to construct a scenario in which Venus started out like the Earth - possibly including a habitable environment, billions of years ago - and then evolved to the state we see now."

Unlike the Earth, Venus lacks a magnetic shield to protect it from the solar wind, a stream of charged particles ejected from the sun. As a result, hydrogen, helium, and oxygen are blown away from the atmosphere on Venus much faster than on Earth. The scientists believe that Venus may once have had liquid water oceans on its surface which, as a result of the solar wind, were largely removed during the first billion years after the formation of the Solar System. "Eventually the oceans boiled off, and all the water ended up as water vapor in the atmosphere," Svedhem said.

Data from the magnetometer instrument on Venus Express confirm that there is lightning on Venus, a once controversial idea. In fact, the findings suggest that lightning is more common on Venus than on Earth.

Unlike the Earth, Venus has undergone runaway greenhouse warming and now has an average surface temperature of 467 degrees Celsius. Some believe that studying how this change came about could lead to insights into how to prevent undesired climate change on Earth. "Understanding the influencing factors of global warming on Venus could help us in mitigating the threat here on Earth," said United Kingdom Minister for Science and Innovation Ian Pearson.